Link tag helper should include original element's attributes in fallbacks

[dougbu]

E.g. .cshtml contains:

    <link rel="stylesheet" data-extra="test"
          asp-fallback-href="~/styles/site.css"
          asp-fallback-test-class="hidden"
          asp-fallback-test-property="visibility"
          asp-fallback-test-value="hidden">

Generated HTML with a few extra newlines:

    <link rel="stylesheet" data-extra="test">
<meta name="x-stylesheet-fallback-test" content="" class="hidden" />
<script>
!function(a,b,c){
var d,e=document,
  f=e.getElementsByTagName("SCRIPT"),
  g=f[f.length-1].previousElementSibling,
  h=e.defaultView&&e.defaultView.getComputedStyle?e.defaultView.getComputedStyle(g):g.currentStyle;
if(h&&h[a]!==b)
  for(d=0;d<c.length;d++)
    e.write('<link rel="stylesheet" href="'+c[d]+'"/>')
}("visibility","hidden",["\/styles\/site.css"]);
</script>

Note the data-extra is not included in the <link> element in the JavaScript, ready to be written into the document. Should it?

[dougbu]

/cc @DamianEdwards ??

[DamianEdwards]

Given cases like http://codepen.io/tigt/post/async-css-without-javascript where you'd want extra attributes to get different behavior, then yes, it should probably preserve the extra attributes. I actually thought I remembered writing the code to do that... Does it work in the script TH?

[dougbu]

Does it work in the script TH?

For some definition of "work" i.e. modulo #4083, yes.

[NTaylorMullen]

d60ed06